Fluctuation-induced flux at the plasma edge in toroidal devices

Carreras, B. A.; Hidalgo, C.; Sánchez, E.; Pedrosa, M. A.; Balbín, Rosa; Garcı́a-Cortés, I.; Milligen, B. Ph. van; Newman, D. E.; Lynch, V. E.

doi:10.1063/1.871523

Cited by 140 publications

(141 citation statements)

References 23 publications

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“…Similar figures are valid also for tokamaks 2,3 and linear devices 4 . These intermittent events are nowadays associated to coherent structures moving into a background plasma.…”

Section: Introductionsupporting

confidence: 69%

On the probability distribution function of particle density at the edge of fusion devices

2004

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The Probability Distribution Function (PDF) P n (n) of the particle density at the edge of several magnetic fusion devices, including tokamaks, stellarators, and linear devices, is known to be strongly non-gaussian. In this paper we present experimental results from RFX Reversed Field Pinch [G. Rostagni, Fus. Eng. Design 25, 301 (1995)], confirming the universal shape of P n also for RFP's. An explanation for the form of P n is attempted, on the basis of simple conservation equations. The model result is shown to fitted fairly well empirical data in a few different experimental scenarios.

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“…Similar figures are valid also for tokamaks 2,3 and linear devices 4 . These intermittent events are nowadays associated to coherent structures moving into a background plasma.…”

Section: Introductionsupporting

confidence: 69%

On the probability distribution function of particle density at the edge of fusion devices

2004

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“…The observation of the indices a X X ¼ P; P h i; C; C h i ð Þ is compared to theoretical considerations. With the assumption of Gaussian fluctuation fields, the PDF of point-wise C is predicted to have an exponential tail (i.e., a C ¼ 1), 5 while that of P was shown to be a stretched Gaussian with a P ¼ 1.5. 13 Analysis of the flux-averaged particle flux C h i in simulation has suggested a log-normal or extreme value distribution (EVD, Ref.…”

Section: -3mentioning

confidence: 99%

“…Non-Gaussian properties of C and P have been studied theoretically 5,13,14 and experimentally. [4][5][6][15][16][17] Global transport phenomena are determined by the flux events averaged over the flux surface and=or over the full azimuthal direction. To show the evidence of the difference of PDFs between the local one and azimuthally-averaged one, dependence of PDF of azimuthally averaged Reynolds stress (RS) on the number of the RSP is first shown.…”

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confidence: 99%

“…It was pointed out that even if the local density and electric field perturbation obey the Gaussian statistics, the induced local particle flux can show the exponential tail. 5 Although progresses have been noticeable in the experimental study of local particle flux, measurements of the global transport phenomena by turbulence stochasticity are required because relaxation of the far-non-equilibrium media depends upon the global transport of the media. The global momentum flux is essential for the generation of global axial vector field by thermal turbulence (e.g., zonal flow, geo-and astro-dynamo magnetic field, etc).…”

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confidence: 99%

“…Non-Gaussianity of the probability density function (PDF) is one of the key elements that characterize the far-nonequilibrium states. 1,2 Reports were made on the point-wise measured particle flux in turbulent plasmas, [3][4][5][6] where the nonGaussian PDF of particle flux has often been observed. It was pointed out that even if the local density and electric field perturbation obey the Gaussian statistics, the induced local particle flux can show the exponential tail.…”

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Non-Gaussian properties of global momentum and particle fluxes in a cylindrical laboratory plasma

et al. 2011

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Non-Gaussian statistical properties of the azimuthally averaged momentum and particle fluxes driven by turbulence have been simultaneously observed in inhomogeneous magnetized plasmas for the first time. We identified the stretched Gaussian distribution of the both fluxes and the transition from the point-wise distribution to averaged ones was confirmed. The change of the particle flux precedes that of the momentum flux, demonstrating that the momentum flux is induced by the relaxation of density gradient.

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Baffled‐Probe Cluster for Simultaneous, Single‐Point Monitoring of Magnetized Plasma Fluctuations

Koepke

Demidov

Finnegan

et al. 2006

Contrib. Plasma Phys.

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Key words Electric probe, probe array, magnetized plasma, potential and temperature oscillations. PACS 52.70.-m An array of baffled probes for the real-time monitoring of oscillating values of space potential, electric field and electron/ion temperature in magnetized plasma is assembled and tested. The multi-probe array samples a region with dimensions on the order or less than an ion gyroradius, essentially a single point, and does not require voltage sweeps. We refer to an array of probes contained within such a single point as a probe cluster. Here, we describe two versions of the baffled-probe cluster. In the first cluster, four independent coils of collection wire are mounted at 90-degree intervals around the circumference of a short, thin, cylindrical, four-bore ceramic tube. This tube slides into a larger-diameter, single bore, ceramic tube having four azimuthally separated masks (baffles), each lining up with a coil-coil gap on the 4-bore tube, and four baffle-to-baffle gaps, each lining up with a coil on the 4-bore tube. The second cluster uses a single four-bore ceramic tube, with four longitudinal slots to allow side access to each bore, and probes made from a single strand of collection wire. With the tubes oriented perpendicular to the magnetic field, the baffled-probe cluster is rotated around its axis in order to regulate the ratio between electron and ion currents to the baffled probes and, thereby, change the probes' relative sensitivity to space potential and temperature oscillations. This probe-cluster design has the advantages of realtime monitoring of magnetized-plasma fluctuations, post-acquisition determination of electron-temperature or ion-temperature time series, post-acquisition determination of cross-phase and coherence between fluctuations of individual plasma parameters, compact size, minimal plasma perturbation (probes are non-emissive), and relative insensitivity to alignment uncertainty. The clusters have been used for distinguishing temperature fluctuations from potential fluctuations in plasma of the WVU Q-machine.

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Fluctuation-induced flux at the plasma edge in toroidal devices

Cited by 140 publications

References 23 publications

On the probability distribution function of particle density at the edge of fusion devices

On the probability distribution function of particle density at the edge of fusion devices

Non-Gaussian properties of global momentum and particle fluxes in a cylindrical laboratory plasma

Baffled‐Probe Cluster for Simultaneous, Single‐Point Monitoring of Magnetized Plasma Fluctuations

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